A construction project is similar to a big, open house party; during just a few months, subcontractors of every stripe pass through to do their work and collect their pay. There are surveyors, excavators, masons, carpenters, roofers, siding guys, insulation contractors, plumbers, HVAC types and landscapers.
Besides coffee and gasoline, the fuel that keeps them all moving is power in the form of electricity. All the contractors need it to varying degrees and if they don’t get power when they need it, the construction superintendent is going to hear about it. To avoid these unpleasant confrontations, it’s a good idea to know the basics of electricity distribution and how a project interfaces with the local electric utility and the electrical contractors that are going to be onsite.
The Source of Jobsite Power
Except in the case of portable generators, power is manufactured at plants that are often very far away from where it’s going to be used. Once generated, the power goes into step-up transformers that increase the line voltage to 200,000 volts or more. These high voltages make it easier for the power to travel the long distances that are usually required.
This journey is made through high-voltage lines—the type of cables that are supported on large towers, high above the ground. As the power approaches
its destination, it passes into local substations that have step-down transformers. These reduce the line voltage to a level that can be safely distributed throughout the community on wooden (usually) power poles. The last change that’s made is in transformers that are mounted on street poles. These devices reduce the power to 120-volt current, which is designed for residential use.
In a typical detached house, the power comes from the transformer, through the air to a weather head (or service head) that is mounted on the roof and provides a way for the service wires to attach to the electrical circuits inside the house. On many commercial projects, this path from the transformer is made underground, with the service cables coming above ground next to the building.
How Power Is Distributed On a Jobsite
At this point, the utility’s electric meter is attached to the service cables and will measure every bit of electricity that leaves the service lines and enters the building.
New service lines are composed of three individual cables: two power (or hot) lines that each carry 120 volts and a third grounding wire. When the cables enter the service panel inside the house, they are attached to bus bars at the top of the panel. Two vertical buses are designed to hold the power cables, while a third bar, usually off to one side, is where the ground cable is attached. Many times, there are multiple grounding bars to make circuit installations easier.
For regular circuits, such as lights and simple receptacles, 120-volt service is the standard, which is regulated by a single circuit breaker. If more voltage is required (for example, 240 volts for a clothes dryer), double breakers are used to deliver 240 volts (2 x 120).
Who’s In Charge of Electricity On the Jobsite
In most cases, once the utility makes the cable connections at the weather head, the rest of the installation is the project manager’s problem, which means dealing with electrical inspectors. No one doubts the value of properly inspected and approved electrical installations. And everyone knows how important it is to get along with these inspectors.
One of the smartest things a construction manager can do upfront is establish exactly what electrical inspections are required, the inspection timeline, what happens if something doesn’t pass inspection and how responsive inspectors will be to calls from the supervisor and onsite electricians. Get the answers (preferably on paper) before any work begins and consider staying on the inspector’s schedule a very big priority as work proceeds.
Know How to Solve Basic Problems
Not many construction managers are licensed electricians, but sometimes common sense calls for a little more involvement. Following are a few situations construction managers need to know how to handle:
- When ground fault receptacles won’t work in the middle of the day;
- When lights flicker at dusk just when a potential customer is coming to look at the house; and
- When a carpenter is stuck on the roof trying to cut a piece of trim and the power won’t stay on, no matter how much he screams at everybody on the ground.
In these scenarios, it might be time to lend a hand. A few simple tools in the glove compartment can solve a lot of small problems before they get out of hand. Here’s a basic kit:
Current tester
This simple, inexpensive tool has two lead wires with a small neon light in between. It’s made to check for current in receptacles, lights and other simple electric devices. By sticking the lead wires in a receptacle (one in each slot) and looking at the light, you can tell if there is current (the light turns on) or no current (the light doesn’t light).
The same presence of current can be established by touching the white and black wires that power the sides of a light socket. The tester is indispensable from a diagnostic point of view, but, if anything, it’s more important as a safety device. No wire or fixture should ever be touched before checking for current.
Needle-nose pliers
An 8-inch pair of needle nose pliers is a great help in reattaching wires that may have come loose in switches, lights and receptacles. Just use the narrow tips to form a loop on the end of a wire, then attach it by tightening the terminal screw that is designed to hold it in place.
Multi-tip screwdriver
An inexpensive screwdriver with interchangeable tips held inside the handle can make easy work of just about any screws that you are likely to encounter. This tool can tighten most electrical connections, as well as providing access to switches, receptacles and light fixtures.
Wire strippers
This simple tool, shaped like flat pliers, is designed to remove the insulation that covers all wires. About 5/8 inch of this insulation should be stripped from any wire that is attached to other wires with a wire connector or to the back or sides of receptacles and switches.
Electrical tape
Sometimes a temporary splice is the best way out of a tight spot. Seal up your wire connectors with a thorough wrap of electrical tape if you have to provide temporary power in a pinch.
Installing a temporary power pole and securing an electrical connection is often the first step (after the paperwork) on a construction project. As a manager and executive, the more you know about how electricity gets to your project and is then harnessed into a usable form, the more prepared you’ll be to take action when the need strikes.
